I'm trying to make the choice based off my limited experience; my trainer was designed to fly with a .40 - .46 engine. I have a .46 and a guy at the field, who has the same trainer, has a .40 and there's a huge performane difference between our two planes. The Sig 4 Star 60 will be my second plane, which according to Sig runs with a .60 - .75 engine. Following what little I have seen, I think I want an engine in the upper range. Is that reasonable or am I over-thinking . . . again?

Would the OS .91 be an acceptable engine for this plane? With so little experience, I have a tendency to follow the manf. recommendations a little too literaly so I didn't even consider going to a larger engine.